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selftests/powerpc: Add test of memcmp at end of page

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Update our memcmp selftest, to test the case where we're comparing up
to the end of a page and the subsequent page is not mapped. We have to
make sure we don't read off the end of the page and cause a fault.

We had a bug there in the past, fixed in commit
d9470757398a ("powerpc/64: Fix memcmp reading past the end of src/dest").

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200722055315.962391-1-mpe@ellerman.id.au
This commit is contained in:
Michael Ellerman 2020-07-22 15:53:15 +10:00
parent 5c92fb1b46
commit 8ac9b9d61f
1 changed files with 20 additions and 16 deletions
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36
tools/testing/selftests/powerpc/stringloops/memcmp.c
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@ -2,6 +2,7 @@
#include <malloc.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <time.h>
#include "utils.h"
@ -13,6 +14,9 @@
#define LARGE_MAX_OFFSET 32
#define LARGE_SIZE_START 4096
/* This is big enough to fit LARGE_SIZE and works on 4K & 64K kernels */
#define MAP_SIZE (64 * 1024)
#define MAX_OFFSET_DIFF_S1_S2 48
int vmx_count;
@ -68,25 +72,25 @@ static void test_one(char *s1, char *s2, unsigned long max_offset,
static int testcase(bool islarge)
{
char *s1;
char *s2;
unsigned long i;
unsigned long i, comp_size, alloc_size;
char *p, *s1, *s2;
int iterations;
unsigned long comp_size = (islarge ? LARGE_SIZE : SIZE);
unsigned long alloc_size = comp_size + MAX_OFFSET_DIFF_S1_S2;
int iterations = islarge ? LARGE_ITERATIONS : ITERATIONS;
comp_size = (islarge ? LARGE_SIZE : SIZE);
alloc_size = comp_size + MAX_OFFSET_DIFF_S1_S2;
iterations = islarge ? LARGE_ITERATIONS : ITERATIONS;
s1 = memalign(128, alloc_size);
if (!s1) {
perror("memalign");
exit(1);
}
p = mmap(NULL, 4 * MAP_SIZE, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
FAIL_IF(p == MAP_FAILED);
s2 = memalign(128, alloc_size);
if (!s2) {
perror("memalign");
exit(1);
}
/* Put s1/s2 at the end of a page */
s1 = p + MAP_SIZE - alloc_size;
s2 = p + 3 * MAP_SIZE - alloc_size;
/* And unmap the subsequent page to force a fault if we overread */
munmap(p + MAP_SIZE, MAP_SIZE);
munmap(p + 3 * MAP_SIZE, MAP_SIZE);
srandom(time(0));